CN112681339A

CN112681339A - Occlusive pile construction method with independent pilot tunnel

Info

Publication number: CN112681339A
Application number: CN202011582940.8A
Authority: CN
Inventors: 孟祥磊; 刘大鹏; 陈佳鑫; 杨琦; 刘朝; 许汗宸
Original assignee: Beijing Urban Construction Rail Transit Construction Engineering Co ltd
Current assignee: Beijing Urban Construction Rail Transit Construction Engineering Co ltd
Priority date: 2020-12-28
Filing date: 2020-12-28
Publication date: 2021-04-20

Abstract

The embodiment of the invention provides a method for constructing a secant pile with independent pilot tunnels, wherein a retaining wall pile comprises alternately arranged vegetable piles and meat piles, the secant pile is formed by mutually meshing adjacent retaining wall piles, and the formed secant pile is used for excavating a pit foundation retaining wall in an undercut mode, and the method comprises the following steps: excavating a pilot tunnel convenient for the construction of the retaining wall pile before the construction of each retaining wall pile according to the construction sequence of the retaining wall piles; constructing the plain piles according to the construction sequence of jumping from three to one; and a meat pile is arranged between every two adjacent vegetable piles, and the cross section of each meat pile is respectively overlapped with the cross sections of the two adjacent vegetable piles to form mutually meshed secant piles. The pilot tunnel convenient for the construction of the retaining wall pile is excavated before the construction of each retaining wall pile, so that the cost is reduced.

Description

Occlusive pile construction method with independent pilot tunnel

Technical Field

The invention relates to construction of foundation pit retaining wall piles, in particular to a construction method of an occlusive pile with an independent pilot tunnel.

Background

With the acceleration of the urban development process, the development utilization rate of the urban underground space is higher and higher, and in the construction process of the urban underground space structure, the safety of the underground structure construction and the surrounding environment of the foundation pit needs to be ensured, and protective measures are taken for the side wall of the foundation pit and the surrounding environment. In the process of implementing the invention, the applicant finds that at least the following problems exist in the prior art: when the protection structure is arranged on the side wall of the foundation pit, the construction cost of the foundation pit retaining wall is higher.

Disclosure of Invention

The embodiment of the invention provides a method for constructing an occlusive pile with independent pilot tunnels, which is used for reducing the cost by excavating the pilot tunnels convenient for the construction of the retaining wall piles before the construction of each retaining wall pile.

In order to achieve the above object, an embodiment of the present invention provides a method for constructing a secant pile with independent pilot tunnels, where a retaining wall pile includes alternately arranged plain piles and meat piles, adjacent retaining wall piles are meshed with each other to form the secant pile, and the formed secant pile is used for excavating a pit foundation retaining wall, where the method includes:

excavating a pilot tunnel convenient for the construction of the retaining wall pile before the construction of each retaining wall pile according to the construction sequence of the retaining wall piles;

constructing the plain piles according to the construction sequence of jumping from three to one; wherein, the three-to-one jumping means: in the first round of plain pile construction process, construction is carried out at intervals of 3 plain pile positions to form a plurality of first plain piles in sequence; in the second round of plain pile construction process, constructing the middle plain pile position in 3 plain pile positions at intervals according to the first round of plain pile construction sequence direction to form a plurality of second plain piles; in the third round of plain pile construction process, sequentially constructing the rest plain pile points according to the construction sequence direction of the first round of plain piles to form a plurality of third plain piles; all the first plain piles, all the second plain piles and all the third plain piles form all the plain piles of the foundation retaining wall of the underground excavation pit, and two adjacent plain piles are not overlapped with each other;

meat-bearing pile positions are arranged between every two adjacent vegetable piles, and construction is carried out on every two meat-bearing pile positions in the construction process of the first round of vegetable piles according to the construction sequence direction of the first round of vegetable piles to form a plurality of first meat-bearing piles; in the construction process of second round meat-meat piles, according to the construction sequence direction of the first round vegetable piles, a plurality of second meat-meat piles are sequentially constructed at the rest meat-meat pile positions, all the first meat-meat piles and all the second meat-meat piles form all meat-meat piles of the underground excavation pit base retaining wall, and the cross section of each meat-meat pile is respectively overlapped with the cross sections of two adjacent vegetable piles to form mutually-meshed piles.

The technical scheme has the following beneficial effects: the pilot tunnel convenient for the construction of the retaining wall pile is excavated before the construction of each retaining wall pile, so that the cost is reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a method of constructing a bite pile with an independent pilot tunnel according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a retaining wall pile construction sequence according to an embodiment of the present invention;

FIG. 3 is a flow chart of pile-forming construction of plain piles and a flow chart of pile-forming construction of double-layered piles according to the embodiment of the present invention;

FIG. 4 is a retaining wall cross-sectional view of a retaining pile of an embodiment of the present invention;

FIG. 5 is a process diagram of straight threads of reinforcement bars for a reinforcement cage according to an embodiment of the present invention;

FIG. 6 is a schematic view of a rebar head on a rebar cage according to an embodiment of the invention;

FIG. 7 is a view showing the installation position of a pile bottom grouting pipe according to an embodiment of the present invention;

FIG. 8 is a diagram of a pile side grout pipe installation location of an embodiment of the present invention;

FIG. 9 is a verticality detecting instrument;

FIG. 10 is a schematic diagram of the perpendicularity detecting instrument of FIG. 9;

FIG. 11 is a result of a test using the verticality testing apparatus of FIG. 9;

FIG. 12 is a borehole electromagnetic wave imaging apparatus;

FIG. 13 is a diagram of FIG. 12 illustrating the detection principle of the borehole electromagnetic wave imaging apparatus;

fig. 14 is a view showing a result of the detection using the electromagnetic wave imaging apparatus for borehole in fig. 12.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, in combination with an embodiment of the present invention, there is provided a method of constructing a spud pile with independent pilot tunnels, the retaining wall pile including alternately arranged plain piles and meat piles, the spud pile being formed by adjacent retaining wall piles being mutually spud, the formed spud pile being used for excavating a pit foundation retaining wall, the method including:

meat-bearing pile positions are arranged between every two adjacent vegetable piles, and construction is carried out on every two meat-bearing pile positions in the construction process of the first round of vegetable piles according to the construction sequence direction of the first round of vegetable piles to form a plurality of first meat-bearing piles; in the construction process of second round meat-meat piles, according to the construction sequence direction of the first round vegetable piles, a plurality of second meat-meat piles are sequentially constructed at the rest meat-meat pile positions, all the first meat-meat piles and all the second meat-meat piles form all meat-meat piles of the underground excavation pit base retaining wall, and the cross section of each meat-meat pile is respectively overlapped with the cross sections of two adjacent vegetable piles to form mutually-meshed piles. The pilot tunnel convenient for the construction of the retaining wall pile is excavated before the construction of each retaining wall pile, so that the cost is reduced.

Preferably, the excavating of the corresponding pilot tunnel before the construction of each occlusive pile according to the construction sequence of each retaining wall pile comprises:

classifying a plurality of adjacent retaining wall piles according to the shape of the retaining wall of the foundation pit, the size of the retaining wall, the number of the retaining wall piles, the positions of the retaining wall piles and the construction sequence of the retaining wall piles to form a plurality of retaining wall pile groups, wherein the same retaining wall pile group shares the same pilot tunnel;

when excavating the pilot tunnel, according to the construction sequence of the retaining wall piles, firstly excavating the same common pilot tunnel to the first constructed retaining wall pile in the retaining wall group, or enabling the same common pilot tunnel to pass through the first constructed retaining wall pile in the retaining wall group;

and when the pilot tunnel is excavated, the ring beam and the grid are welded to reinforce the pilot tunnel being excavated.

Preferably, when excavating the pilot tunnel, the method of reinforcing the pilot tunnel being excavated by welding the ring beam and the grating includes:

firstly, arranging grids at the excavation position of a pilot tunnel, grouting outside the grid breaking range, breaking the grids after grouting is finished, breaking openings with the diameter of 1.4m and the depth of 0.25m, and constructing reinforced concrete ring beams at the openings; and when the opening is broken, the longitudinal ribs of the grating which do not cut off the excavation direction along the pilot tunnel and do not influence the pilot tunnel protection wall are reserved.

Preferably, the construction of the plain piles is carried out according to a construction sequence of jumping from three to one, and the construction method specifically comprises the following steps:

when any one pile position is constructed, digging a hole in the pile position from top to bottom manually, and forming a first digging section when the pile is dug to a first preset depth; arranging a retaining wall for the plain pile at the first section of excavation, wherein the retaining wall of the plain pile is arranged outside the diameter of the plain pile and is attached to and wound on the plain pile; the protecting wall of the plain pile is formed by pouring concrete and tamping;

after the concrete of the retaining wall of the first section of plain pile reaches a first preset strength, continuing to dig a hole downwards to form a second section of excavation, and arranging a retaining wall for the plain pile in the second section of excavation, wherein the retaining wall of the plain pile is arranged outside the diameter of the plain pile and is attached to and wound on the plain pile; the protecting wall of the plain pile is formed by pouring concrete and tamping;

after the concrete of the retaining wall of the second section of plain pile reaches a second preset strength, drilling downwards by a drilling machine;

when drilling, pumping out slag slurry from the pile holes by a pump suction reverse circulation process of a drilling machine and discharging the slag slurry into a slag slurry special pool by a sand pump; simultaneously, inputting the prepared slurry into the plain pile hole from the slurry tank, and ensuring that the slurry surface in the plain pile is higher than the preset height of the top surface of the protecting wall of the plain pile;

after the slurry pumped out from the plain pile hole is discharged to the slurry special tank, pumping the light slurry on the upper layer of the slurry into a slurry purification device through a slurry pump; filtering sand and impurities in the light slurry by a slurry purification device to improve, so as to obtain improved high-quality slurry; discharging the improved high-quality slurry into a slurry pool;

reaching the preset depth of the plain pile along with the downward drilling of the drilling machine;

and cleaning the drilled holes twice, and detecting whether the slurry index and the sediment thickness in the plain pile hole meet the relevant standards after cleaning the holes until a qualified plain pile drilled hole is formed.

aiming at any plain pile, after the plain pile is drilled, a guide pipe is installed in the drilled hole, the guide pipe is connected through a plurality of sections of pipeline joints, and the joint of each pipeline joint is tested through a water-proof bolt, so that the guide pipe is ensured not to leak water; the bottom of the bottom section guide pipe positioned at the bottom of the drill hole is not provided with a flange, and the length of the bottom section guide pipe is longer than that of the rest guide pipes by a preset length; the distance from the bottom end of the bottom section conduit to the bottom of the drill hole is 30-50 cm;

conveying concrete into the guide pipe by a concrete conveying pump to pour the concrete into the drill hole; in the pouring process, the depth of the embedded concrete of the bottom section conduit is 2-3m, and the conduit is lifted along with pouring and the redundant conduit is removed;

in the concrete pouring process, controlling the burial depth of the guide pipe in the concrete within a preset range according to the pouring requirement; when the buried depth of the conduit exceeds the maximum value of the preset range, the buried depth of the conduit in the concrete is controlled within the preset range by removing the conduit.

Preferably, the construction in proper order at meat stage pile position forms meat stage pile, specifically includes:

when any meat pile position is constructed, digging a hole in the meat pile position from top to bottom, wherein the hole digging comprises the step of hollowing out the section of a vegetable pile lapped with the meat pile; when the excavation is carried out to a first preset depth, an excavation first section is formed; arranging a retaining wall for the meat-bearing pile at the first stage of excavation, wherein the retaining wall of the meat-bearing pile is arranged outside the diameter of the meat-bearing pile and is attached to and wound around the meat-bearing pile; the protecting wall of the meat pile is formed by pouring concrete and tamping;

after the concrete of the retaining wall of the meat-bearing pile at the first section reaches a first preset strength, continuing to dig a hole downwards to form a second section of excavation, and arranging a retaining wall for the meat-bearing pile at the second section of excavation, wherein the retaining wall of the meat-bearing pile is arranged outside the diameter of the meat-bearing pile and is attached to and wound on the meat-bearing pile; the protecting wall of the meat pile is formed by pouring concrete and tamping;

after the concrete of the retaining wall of the second section of meat-bearing pile reaches a second preset strength, drilling downwards through a drilling machine;

when drilling, pumping the slurry from the holes of the meat-bearing piles by a pump-suction reverse circulation process of a drilling machine and discharging the slurry into a slurry special tank by a sand pump; meanwhile, the prepared slurry is input into the holes of the meat-bearing piles from the slurry tank, and the slurry surface in the meat-bearing piles is higher than the preset height of the top surfaces of the retaining walls of the meat-bearing piles;

after the slurry pumped from the holes of the meat piles is discharged to the slurry special tank, pumping the light slurry on the upper layer of the slurry into a slurry purification device by a slurry pump; filtering sand and impurities in the light slurry by a slurry purification device to improve, so as to obtain improved high-quality slurry; discharging the improved high-quality slurry into a slurry pool;

the preset depth of the meat pile is reached along with the downward drilling of the drilling machine;

and (3) cleaning the drilled holes twice, and detecting whether the slurry index and the sediment thickness in the meat pile hole meet the relevant standards after cleaning the holes until a qualified drilled hole of the meat pile is formed.

aiming at any meat pile, after drilling the meat pile, sequentially conveying a plurality of sections of steel frameworks forming a steel reinforcement cage to the position above a drilling hole of the meat pile, lowering a first section of steel framework into the drilling hole of the meat pile, and when a last section of stiffening rib of the first section of steel framework is positioned above the drilling hole of the meat pile, penetrating a last section of stiffening rib into an I-shaped steel, and supporting the first section of steel framework on the I-shaped steel; hoisting a second steel skeleton to enable the second steel skeleton and the first steel skeleton to be located on the same vertical axis, and connecting the second steel skeleton and the first steel skeleton by a sleeve; drawing out I-shaped steel from the position of the last section of stiffening rib of the first section of steel framework; placing the connected second steel skeleton and the first steel skeleton in the hole drilled by the meat pile;

when the last stiffening rib of the second steel skeleton lifted after hoisting is positioned above the pile hole, the I-steel penetrates into the last stiffening rib of the second steel skeleton installed after hoisting; hoisting a third steel skeleton to enable the third steel skeleton and the second steel skeleton to be positioned on the same vertical axis, and connecting the second steel skeleton and the third steel skeleton by a sleeve;

and circulating the steps, connecting the steel frameworks lifted in sequence to the previous steel frameworks and placing the steel frameworks into the drilled hole in sequence until the last section of framework is placed at the designed elevation of the retaining pile and the axis of the last section of framework is positioned in the center of the hole opening, and finishing the installation of the reinforcement cage.

Preferably, the method further comprises the following steps:

after the reinforcing cage of the meat pile is installed, a guide pipe is arranged in a drill hole of the concrete meat pile, the guide pipe is connected through a plurality of sections of pipeline joints, and the water leakage of the guide pipe is ensured through a test of a water-isolating bolt on the joint of each pipeline joint; the bottom of the bottom section conduit at the bottom of the drilling hole of the meat pile is not provided with a flange, and the length of the bottom section conduit is longer than that of the rest conduits by a preset length; the distance from the bottom end of the bottom section conduit to the bottom of the drill hole is 30-50 cm;

conveying concrete to the guide pipe through a concrete conveying pump and pouring the concrete into the drilled hole of the meat pile; in the pouring process, the depth of the embedded concrete of the bottom section conduit is 2-3m, and the conduit is lifted along with pouring and the redundant conduit is removed;

in the concrete pouring process, controlling the burial depth of the guide pipe in the concrete within a preset range according to the pouring requirement; when the buried depth of the guide pipe exceeds the maximum value of the preset range, the buried depth of the guide pipe in the concrete is controlled within the preset range by removing the guide pipe;

when the concrete reaches the preset strength, the meat-bearing pile is formed.

Preferably, the method further comprises the following steps:

aiming at meat piles, when a reinforcement cage is installed, three pile bottom grouting pipes are arranged in the reinforcement cage, and are uniformly arranged on the inner sides of inner reinforcing stirrups of steel frames; outside the steel reinforcement cage, two pile side grouting pipes are arranged at the junction lap joint of the meat-bearing pile and any adjacent vegetable pile, and the two pile side grouting pipes are arranged outside the steel skeleton;

all pile bottom grouting pipes and pile side grouting pipes are respectively spot-welded and tightly bound with main reinforcements of the steel framework; the pile bottom mud jacking and grouting pipes are connected by screw threads; the bottom of the pile bottom grouting pipe extends out of the first steel skeleton by 300 mm; the pile side grouting pipes are connected by screw threads, and drill holes are arranged at intervals of a preset distance on the pipe walls of the pile side grouting pipes;

the bottoms of all pile bottom grouting pipes and pile side grouting pipes are tightly wrapped;

and after the meat-bearing pile is formed into a pile for 14 days, grouting is respectively carried out through a pile bottom grouting pipe and a pile side grouting pipe;

before grouting, the smooth conditions of a pile bottom grouting pipe and a pile side grouting pipe are checked through a pressurized-water test, the smooth conditions of the pile bottom grouting pipe and the pile side grouting pipe are ensured, and simultaneously sediment and slurry in concrete around a one-way grouting valve arranged at a drilling hole of a meat pile are removed;

and during grouting, grouting is carried out by adopting a low-speed and slow-pressing method, cement paste with the water-cement ratio of 0.8-1.0 is pressed into the meat-quality pile, and soil bodies at the end of the meat-quality pile or on the periphery of the meat-quality pile are gradually filled with cement paste.

Preferably, the cross-section of each meat stake overlaps respectively with two adjacent vegetable stake cross-sections, includes:

the lap length between each meat pile and one engaged vegetable pile is 1/5-1/4 of the diameter of the retaining wall pile; and/or the presence of a gas in the gas,

each meat pile and the centers of the two vegetable piles which are engaged with each other form a straight line.

The above technical solutions of the embodiments of the present invention are described in detail below with reference to specific application examples, and reference may be made to the foregoing related descriptions for technical details that are not described in the implementation process.

The invention relates to a construction method for a hard cutting secant pile in a small pilot tunnel, wherein a retaining wall pile is in the form of a secant pile, the secant pile is used as a wall of an undercut foundation pit, the secant pile is formed by overlapping and meshing the cross sections of a vegetable pile and a meat pile, water seepage can be prevented, and the construction process of the wall of the undercut foundation pit is as follows:

during the secant pile construction, need adopt "jump three and play one" construction, guarantee that overlap joint length is 300mm during the adjacent stake position of construction, as shown in fig. 2, construction sequence:

constructing primary plain piles … … S34, S38 and S42 … … (the ellipses represent pile positions in pile jumping sequence, the same below)

Construction of second plain pile … … S36, S40 … …

Constructing the plain piles … … S35, S39, S37 and S41 … … for the third time

Construction of first-pass meat piles … … BH35, BH37, BH39 and BH41 … …

Construction of secondary meat piles … … BH36, BH38, BH40 and BH42 … …

As shown in fig. 3, the construction process of the vegetable pile and the meat pile is shown, wherein the piles in the I-order are vegetable piles, the piles in the II-order are meat piles, and the cross-sectional dimension of the top surface of each retaining wall pile is adopted

1200mm secant pile.

The construction method of the secant pile comprises the following specific steps:

1. in-hole mechanical pile orifice reinforcement

(1) Before construction, a hole opening test is carried out, according to the field hole opening test, the hole opening slotting mode is optimized to be that pilot pits (namely pilot holes) are excavated according to the pile jumping construction sequence, and the pilot pits are reinforced in a mode that ring beams and grids are welded.

(2) Constructing the opening of the occlusive pile according to the pile jumping construction sequence, rechecking the pile position before construction, namely, determining cross control pile lines which are vertical to each other by taking the pile position as the center, wherein the diameter of the opening is 1400 mm;

(3) and (3) before the grids are broken, grouting is carried out outside the broken range of the grids, grouting pipes are DN32 guide pipes with the length of 2m, the angle is an outward inclination of 45 degrees, the grids are broken after grouting is finished, the broken holes have the diameter of 1.4m and the depth of 0.25m, and the reinforced concrete ring beams are constructed. When the hole is artificially broken, the longitudinal bars of the grating which do not affect the digging hole protecting wall are kept as much as possible without cutting off, and 8 holes are used for the edge guide hole

Annular reinforcing steel bars (divided into an upper layer, a middle layer and a lower layer) are welded into a ring in an overlapping mode, and the diameters of the annular reinforcing steel bars are 1.17m, 1.25m and 1.33m respectively; and the grid longitudinal bar is firmly welded with the grid of the bottom plate of the guide hole. Two channels are arranged between each two grid steel frames

The stirrup and the double-layer reinforcing steel bar of the later construction hole pass through three channels

The stirrups are tied on the hole reinforcing ribs and the through grid longitudinal ribs which are constructed firstly, and C25 concrete is poured after the annular reinforcing steel bars are welded firmly.

(4) The depth of the manual hole digging retaining wall is 2m, and the hole digging retaining wall is excavated in two sections, wherein each section is 1 m. The top of the retaining wall is 15cm thick, and the bottom of the retaining wall is 10cm thick. The range of the excavation area is the designed pile diameter plus the thickness of the retaining wall. The soil excavation is carried out from top to bottom manually, and the soil excavation sequence is from the middle to the periphery. And after the wall is dug, manually pouring and manually tamping concrete to pour. The retaining wall concrete is C25 concrete, the slump is controlled to be 80-100 mm, the stability of the hole wall is ensured, and the manual hole digging and retaining wall of side piles (retaining wall piles) is shown in figure 4.

2. Drilling in

After the opening section of the mechanical pile in the hole is finished for 3 days, the strength of the concrete of the retaining wall reaches 75 percent, the concrete is drilled and piled, and a sixth generation crawler-type hydraulic high-power drilling machine of DKZ-8 is adopted to drill holes.

(1) Reverse circulation rotary drilling

1) The principle of reverse circulation work: and drilling is carried out by adopting a pump suction reverse circulation process. Before drilling each pile, preparing slurry according to 1.5 times of the volume of the pile body. When the drilling machine drills a hole, the slurry pumped out from the pile hole by the drill rod is discharged into a slurry pool (slurry special pool) through a sand pump. After the sedimentation, the upper layer of light mud is pumped into the ground mud purification device by a mud pump. The mud purifying device filters sand and impurities in the mud, improves the toughness of the wall protection mud and improves the mud performance. Discharging the improved high-quality slurry into a ground slurry storage pool, and then delivering the high-quality slurry into the pile hole through a slurry pump to realize the balance of the slurry in the hole.

2) The mud circulating system is arranged and used: the device consists of a mud pool, a sand pump, a grouting pump, a deslagging device and the like, and is provided with facilities for draining, cleaning, discharging waste slurry and the like. And the circulating system adopts a pumping recharging type. The number of the mud tanks is 80-120 m, and the volume of each tank³。

3) And after drilling and pore forming, ensuring that the slurry in the pores is sufficient, and the water level of the slurry is 15cm higher than the top surface of the artificial retaining wall so as to ensure that the pore walls do not collapse.

According to the engineering geological condition, high-quality clay is selected for pulping, and a proper amount of bentonite admixture with high montmorillonite content is added when necessary, as shown in tables 1 and 2.

TABLE 1 mud ratio

Item	Water (W)	Nano bentonite	Caustic soda
				Unit of	KG	KG	According to the weight of the soil
Number of	1000	250	2％

TABLE 2 slurry control index

Order of item	Item	Performance index	Instrument for test
				1	Specific gravity of	1.05～1.10	Mud proportion scale
2	Viscosity of the oil	18～25s	500/700ml funnel method
				3	Sand content	＜3％	Sand content measuring instrument
4	Colloidal fraction	>95％
				5	Water loss amount	＜30ml/30min

The specific gravity of the slurry is controlled to be 1.1-1.15 when the slurry passes through a sand-gravel layer or a soil layer easy to collapse for hole forming. After drilling and pore-forming, the mud in the hole is ensured to be sufficient, and the liquid level of the mud is slightly higher than the top surface of the artificial retaining wall, so as to ensure that the hole wall does not collapse.

4) Pumping reverse circulation drilling operation key points:

the connection of the water absorption system needs to be strict, firm and smooth.

The joint part from the suction inlet of the sand pump to the suction inlet of the drill bit comprises a hose, a water tap and a drill rod, all the joint parts are sealed by rubber pads (or rings), all the bolts of the flange are screwed tightly and consistently, so that sundries cannot block the drill slag from passing through the flange, and a certain curvature radius is ensured at the turning place, and a right-angled bend cannot be turned.

Secondly, the drill bit can not be directly lowered to the bottom of the hole when the sand pump is started, and the drill bit is lifted away from the drilling slag at the bottom of the hole for at least keeping a distance of more than 0.2m before the sand pump is started, so that the blockage of a slag suction port of the drill bit is prevented.

Thirdly, the operations of connecting a drill rod, suspending drilling or lifting the drilling tool are performed: and after the rotation of the drilling machine is stopped, the reverse circulation is still maintained for 1-2 min, and after all the drilling slag sucked into the drill rod is discharged out of the ground surface, the sand-stone pump is stopped, so that the situation that the pump is stopped too early and the drilling slag in the drill rod falls to a suction port of a drill bit to form blockage is prevented.

Fourthly, the method for controlling the drilling speed comprises the following steps: A. when drilling in sandy soil or a sandy soil layer containing a small amount of gravels and pebbles, the rotating speed and the footage speed cannot be too high, so that the blockage of a water suction port of a drill bit or the blockage of a slag discharge pipeline is prevented. B. When the silt soil layer which contains abundant water and is easy to collapse is encountered, the silt soil layer needs to be drilled at a slow rotating speed so as to reduce the stirring of the silt soil layer, and meanwhile, the footage speed is increased so as to pass through the silt soil layer quickly and avoid reaming or collapse. If the rated flow of the pump is much larger than the actual flow, the opening of the outlet valve of the sand pump can be reduced, and the flow is controlled, so that the flushing of flushing liquid on the hole wall is reduced.

When a fault or abnormal condition occurs during drilling, stopping to check and search the reason, and continuing drilling after treatment.

(2) Quality inspection of pore formation

The quality of pore-forming is checked during final pore-forming or in the pore-forming process, and the main checking contents are as follows: hole depth, aperture, perpendicularity, hole wall integrity and sediment thickness.

The detection method comprises the following steps: the use of tools, operating methods (in conjunction with the job site) and tolerances meet the specifications set forth in table 3 (see the relevant specifications).

TABLE 3 pore-forming quality test items and requirements

15

(3) Hole cleaning and sediment detection

1) The hole cleaning of the cast-in-situ bored pile is carried out twice. And primary hole cleaning is carried out when the final hole is formed, and secondary hole cleaning is carried out after the steel reinforcement cage and the pouring guide pipe are installed and before concrete pouring.

2) And the hole cleaning adopts pump suction reverse circulation hole cleaning. The method comprises the following steps:

firstly, cleaning the hole for the first time, lifting the drill bit 500-800 mm away from the bottom of the hole, idling by using a drilling tool, inputting high-quality slurry with the sand content of less than 4%, and discharging the slurry containing drilling slag until the hole cleaning requirement is met.

And secondly, cleaning the hole by using a perfusion catheter. And (4) connecting the hole cleaning equipment to the duct port, and connecting high-pressure air through a high-pressure air pipe to form a hole cleaning system.

The discharge amount of the sand pump is equivalent to the input amount of slurry, the water level in the hole is kept, and the collapse of the hole wall is prevented. Meanwhile, the pump amount should not be too large, so as to prevent the hole wall from being sucked and collapsed.

(3) The slurry index and the sediment thickness are required to be detected after primary hole cleaning and secondary hole cleaning and meet the specification of the table 4.

TABLE 4 sediment thickness after hole cleaning and detection method

(4) After the placement of the reinforcement cage and the perfusion guide pipe is finished, slurry with the slurry specific gravity not less than 1.05 is adopted to replace slurry in the hole.

3. Fabrication and placement of reinforcement cage

(1) Basic requirements

1) The raw material of the reinforcing steel bar can be processed after being qualified by field acceptance and retest. The allowable deviation of the actual weight of the raw material of the reinforcing steel bar from the theoretical weight meets relevant regulations.

2) The reinforcing steel bars are classified and overhead stacked according to batch and specification after entering a field, and the reinforcing steel bars are clearly and properly kept to prevent pollution or corrosion.

3) The welding rod used by the reinforcement cage is selected according to the type of the reinforcement parent metal. HRB400 steel bar welding selects E50 series type welding rod.

4) The sleeve used for the mechanical connection of the reinforcing steel bars is required to have a product certification, and the type, production unit, production date and production batch number capable of tracing the mechanical property and processing quality of the raw material of the product are required to be marked on the certification.

5) The steel bar can be manufactured and processed only after the quality inspectors of the steel bar delivery main package are qualified,

(2) manufacturing step of reinforcement cage

1) The stiffening rib ring (stirrup) is made according to the design size and the position of the main rib is marked on the stiffening rib ring (stirrup).

2) The main ribs are arranged on a flat workbench, and the positions of the stiffening ribs are marked.

3) And aligning the mark of any main rib on the stiffening rib with the mark of the stiffening rib in the middle of the main rib, and righting the stiffening rib, enabling the stiffening rib to be vertical to the main rib and then carrying out spot welding. And (4) sequentially manufacturing, and welding all stiffening ribs on one main rib.

4) And (4) rotating the framework by one person at each of two ends of the framework, and welding the other main ribs one by one according to the method.

5) The framework is placed on the support, the spiral disc ribs are sleeved in the framework, the spiral ribs are distributed according to the designed position, and then spot welding is performed firmly.

(3) Technical requirements for processing reinforcement cage

1) The longitudinal main reinforcement joints of the side piles are connected by primary mechanical joints, the straight thread sleeves are locking female sleeves, and the specific section positions are determined according to actual site construction except for the marks in the drawing; the longitudinal bars are connected with the spiral stirrups and the stiffening stirrups by spot welding; the spiral stirrup is welded in an overlapping manner and is welded on one side for 10 d; the main reinforcement at the lower end of the reinforcement cage is inwards folded at an angle of 1:10, and the inward folding range is 500 mm.

2) Oil stains, paint stains, cement paste, floating skin, rust and the like on the surface of the steel bar are to be removed.

3) The surface of the processed steel bar should not have a flaw weakening the section of the steel bar.

4) The main reinforcement of the reinforcement cage is mechanically connected, and the main reinforcement joint is a primary joint.

5) The manufacturing tolerances should meet design and specification requirements.

(4) Construction process for straight thread of reinforcing steel bar

1) The steel bar straight thread preprocessing is carried out on the steel bar processing shed, and the construction procedure is shown in figure 5.

2) Cutting and blanking

The steel bars with non-straight ends are straightened in advance, according to the regulation requirement, the end faces of the notches are perpendicular to the axis and do not have horseshoe shape or deflection, so that the blade type cutting machine and the oxygen blowing cutting machine can not meet the requirement of processing precision, and the steel bars are cut one by one according to the length of the ingredients only by adopting a grinding wheel cutting machine.

3) Processing thread end

The processing process of the filament head comprises the following steps: clamping a steel bar to be processed on a bench clamp of the equipment, starting a machine, pulling a feeding device, moving a power head forwards, starting rib stripping and thread rolling, automatically stopping the equipment and reversing after the steel bar is rolled to a set position, withdrawing the end part of the steel bar from the power head, pulling the feeding device to reset the equipment, and finishing processing the steel bar thread head.

Secondly, when the filament head is processed, water-soluble cutting fluid is adopted, and when the temperature is lower than 0 ℃, 15-20% of sodium nitrite is doped. Machine oil is strictly forbidden to be used as cutting fluid or the cutting fluid is not added for processing the filament head.

And thirdly, the steel reinforcement cage is connected by adopting a locking nut type sleeve, the processing length of the screw head of the locking nut is the sleeve length plus the locking nut length, the length of the sleeve of 1/2 is the other end of the locking nut, and the tolerance of the length of the sleeve is plus 2P (P is the thread pitch).

And fourthly, the operating worker should check the processing quality of the thread heads according to the requirements of the following table, and the thread heads are checked once by using a go-no-go ring gauge every 10 thread heads are processed.

And fifthly, randomly sampling qualified thread heads by a professional quality inspector at the department of project for inspection, cutting off unqualified thread heads, finding out reasons, solving the problems, and then re-processing threads.

Sixthly, the qualified silk heads are protected, the end heads are provided with protective caps or screwed by sleeves, and the silk heads are stacked orderly according to the specification.

4) The thread end run length parameters are shown in table 5.

TABLE 5 DETAIL (STRAIGHT) THREAD HEAD PROCESSING LENGTH PARAMETER

Specification of reinforcing bar	Effective number of complete thread ends
		Φ16	8
Φ18	9
		Φ20	10
Φ22	11
		Φ25	10
Φ28	12

5) The quality inspection method and requirements of the reinforcing steel bar thread head are shown in table 6.

TABLE 6 method and requirements for quality inspection of steel bar ends

Note: the length inspection requirement of a screw head at one end of the locking nut is as follows: sleeve length + locknut length, tolerance +2P (P is pitch)

6) In-situ connection construction

When the reinforcing steel bar is connected, the specification of the reinforcing steel bar and the specification of the sleeve are required to be consistent, and screw threads of the reinforcing steel bar and the sleeve are clean and intact.

And secondly, when the embedded joint is adopted, the position, specification and quantity of the connecting sleeve meet the design requirements. The steel bar with the connecting sleeve is firmly fixed, and the exposed end of the connecting sleeve is provided with a protective cover.

And thirdly, the rolled straight thread joint is constructed by using pipe tongs and a torque wrench, two steel bar screw heads are mutually tightly propped at the middle position of the sleeve, and the precision of the torque wrench is +/-5 percent.

Fourthly, the screwed rolled straight thread joint is painted with red paint for marking, and the length of the single-side exposed screw thread is not more than 2P.

(5) Hoisting of steel reinforcement cage

The steel reinforcement cage is at the hoist and mount in-process, in order to guarantee steel reinforcement cage quality, must pay attention to the protection to the steel reinforcement cage in the transportation, must not warp. And a steel reinforcement cage is hoisted in the pilot tunnel by adopting a straightener, and the sections are connected by adopting straight threads. In order to ensure the quality requirement of the reinforcement cage, a reinforcing measure is adopted in the transfer process to ensure that the reinforcement cage is not deformed. And (5) checking the verticality after the steel reinforcement cage is vertical. After the framework enters the orifice, the framework is righted and slowly lowered, the steel reinforcement cage is strictly forbidden to swing to collide the hole wall, and the inner support is removed and the inner inclined support is strictly forbidden to fall into the hole while lowering.

When the first section of steel framework is lowered to the position of the last section of stiffening rib, I-shaped steel penetrates into the first section of steel framework, the reinforcing rib is supported on the I-shaped steel of the orifice, then the second section of steel framework is lifted, the first section of steel framework and the second section of steel framework are connected on the same vertical axis through a sleeve, and the framework is lowered after the supporting I-shaped steel is drawn out. And circulating the steps, so that the framework is placed to the designed elevation and positioned on the center of the hole, and the installation of the reinforcement cage is completed.

4. Pouring of concrete

After the reinforcement cage is installed, concrete should be poured. The side pile meat pile is made of C30 concrete. The concrete transportation adopts a pumping mode, and the slump is 180-220 mm. In addition, the vegetable piles are cast by C5 plastic concrete, and the pouring process is the same as that of the meat piles.

(1) Before pouring the pile core concrete, cleaning the deficient soil at the bottom of the hole again, removing accumulated water, checking the quality of the hole and the steel reinforcement cage, and pouring the concrete after the supervision and acceptance. And completing the concrete pouring at one time.

(2) Underwater irrigation

1) And arranging a guide pipe, and forming by using a steel pipe with the diameter of 300 mm. The pipe joints are tightly and firmly connected, and the water-proof bolts are spliced and numbered by trial before use and pass a test to ensure that the conduit is watertight. The bottom section of the conduit can be properly lengthened, the bottom is not provided with a flange to prevent the steel reinforcement cage from being dragged, and the rest conduits are 2 m/section. The distance between the bottom end of the conduit and the bottom of the hole is kept 30-50 cm. The depth of the conduit embedded into the concrete in the pouring process is kept to be 2-3m, the conduit is detached along with lifting, and the conduit cannot collide with a reinforcement cage when being lifted and hoisted.

2) Pouring underwater concrete:

firstly, when the first batch of concrete is poured, in order to ensure that the water in the conduit can be completely extruded out by the first batch of concrete and meet the requirement of the primary embedding depth of the conduit (1-1.5m), the minimum capacity of a funnel and a storage device is calculated, a side pile leak hole is provided with a partition plate, and a middle pile funnel is provided with a water-isolating bolt.

Secondly, after the first batch of concrete is poured, continuous pouring is needed, and the interval time for dismantling the guide pipe is shortened as much as possible. In the concrete pouring process, a field technician needs to work for a long time and has a deep hole, grasps the buried depth of the guide pipe, and strictly controls the buried depth of the guide pipe according to the technical specification requirements (the buried depth of the guide pipe is controlled to be 2-6 meters, and is adjusted within the range of 2-6 meters according to different hole diameters and pouring speeds). When the buried depth of the conduit exceeds the specification, the conduit must be removed in time.

Thirdly, in the process of pouring concrete, the quality of the concrete is strictly controlled, the slump is controlled to be 220mm in volume and the slump is ensured to be indiscriminate.

And fourthly, accurately measuring the height from the top surface of the concrete to a reference surface before the guide pipe is removed, calculating the buried depth of the guide pipe, determining the pipe removal length, and rechecking whether the buried depth after the pipe removal meets the technical specification requirement or not by subtracting the removed length of the guide pipe from the total length of the guide pipe. The phenomenon of catheter over-depth or lift-off is absolutely not allowed. When the conduit is dismantled, whether the production of concrete is suspended can be determined according to the specific situation on site. After the catheter is removed, a field technician should check the conditions within the catheter.

And fifthly, in the pouring process, the appointed special person is responsible for filling in the underwater concrete pouring record.

Please supervise the whole process of side-station perfusion.

And seventhly, keeping the concrete test piece 2 groups in each pile when concrete is poured.

(3) Pouring the concrete to the designed elevation of the pile top without scum, silt and the like.

5 grouting reinforcement measure

In order to enhance the bearing capacity and lateral frictional resistance of the pile foundation base and improve the bearing capacity and the occlusion water stop effect of the pile foundation, a measure of grouting reinforcement of an occlusion pile is adopted between the pile bottom and two piles.

1) Grouting pipe arrangement

During the construction of the secant pile, after the holes of the piles in the II sequence are formed, as shown in figure 7, 3 pile bottom grouting pipes (DN32 multiplied by 2.75 steel pipes) are arranged in the reinforcement cage, and are arranged on the inner side of the reinforcement stirrup of the reinforcement cage in an equilateral triangle; as shown in fig. 8, 4 pile-side grouting pipes (DN32 × 2.75 steel pipes) are arranged outside the reinforcement cage and at the junction with the I-sequence plain pile. And the grouting pipes are all placed down along with the reinforcement cage and are in spot welding and tight binding with the main reinforcement of the reinforcement cage. The grouting pipes are connected by screw threads, so that welding is avoided, and the grouting pipes are lowered to the bottom of the hole section by section. The bottom of the pile bottom mud jacking and grouting pipe extends out of the reinforcement cage by 300 mm. Drilling holes at intervals of 2m on the pipe wall of the pile side grouting pipe, and tightly wrapping the bottom of the grouting pipe to prevent concrete from entering the grouting pipe in the grouting process.

When each grouting pipe is placed down along with a reinforcement cage, a water test is carried out, and if water columns or water columns disappear, whether the grouting pipes have sand holes or not and whether the screw thread connection is sealed or not is checked; and the grouting pipe and the main reinforcement of the reinforcement cage are spot-welded and tightly bound.

2) Grouting method

And grouting is started after the second-order pile is formed for 14 days generally. Before formal grouting, a pressurized water test is required, and the pressurized water test mainly aims to check the smoothness of a pipeline and a one-way valve and simultaneously remove sediments and slurry in concrete around the one-way valve.

The grouting slurry is cement slurry, the water cement ratio is 0.8-1.0, and the grouting adopts a low-speed and slow-pressing method. The grouting pile can prevent the situation that the pressure is suddenly increased and the grouting can not be performed, and can also prevent grout from jumping up along the pile body or from overflowing from other places, so that the soil body at the pile end or around the pile is gradually filled with the cement grout, and the pressure naturally forms the condition of gradually increasing along with the increase of the grouting amount. During grouting, a one-way grouting valve is additionally arranged at the orifice, so that grout cannot be poured into the valve during pile body concrete pouring, and the grout cannot flow back during grouting.

The grouting parameters are reasonably selected according to geological conditions, and if the pile end is a compact gravel or pebble bed, the large grouting amount and the larger grouting pressure can be considered, and the grouting amount is taken as a main control index; if the pile side is a compact sandy soil layer, the grouting pressure can be used as a main index, and the grouting amount is used as a reference index.

The stratum is mainly a sand layer, and the final pressure is controlled by the mud jacking pressure. The final pressure condition is that the pressure stabilizing pressure is more than 3MPa for 1 min. And immediately screwing a plug on the grouting pipe after grouting to avoid reducing grouting effect due to grouting return.

6. Detection of verticality and occlusion effect

1) Perpendicularity detection

(1) A detection instrument: JL-IUDS (B) intelligent ultrasonic pore-forming quality detector, as shown in FIG. 9.

(2) Detection method

As shown in fig. 10, the lifting structure lowers the acoustic probe from the hole opening to the hole bottom (or lifts the acoustic probe from the hole bottom to the hole opening), and when the instrument is lowered (lifted) and measures a group of (four) acoustic time values at regular intervals as the acoustic time values of the measuring points of the cross section, the recorder (computer) records the acoustic time values of the measuring points at different elevations and calculates the hole diameter of the cross section. When the measuring probe finishes a descending (lifting) process, the recorder (computer) can draw a hole wall section view of the measuring hole. The hoisting point is kept unchanged and the cable is vertical in the lifting (descending) process, and the perpendicularity of the pile hole can be calculated through the measured section view of the wall of the pile hole.

(3) The result of the detection

After the instrument detection is finished, the perpendicularity condition of the pile hole can be visually reflected in a detection report form, as shown in fig. 11.

2) Curtain wall detection

(1) A detection instrument: the borehole electromagnetic wave imaging apparatus is shown in fig. 12.

(2) Detection method

As shown in fig. 13, a PVC/PE pipe equal in length to the plain pile is pre-buried, and four corner points are respectively provided with one pipe with a pipe diameter of 100 mm; fixing the pile on a reinforcement cage of a meat pile and putting down the pile along with the reinforcement cage in sections; one as an ultrasonic signal transmitting hole and one as a signal receiving hole; in order to sample the stability of the data, the probe does not collect the data in the process of lowering, receive the data while lifting, the launcher and receiver are all lowered to the position of pile bottom first, then the receiver receives the signal during the time when the launcher is lifted from the pile bottom to the pile mouth every 1m interval; the influence of the reinforcing steel bars needs to be eliminated through two times of interval measurement, and finally, a leakage point is detected after information is processed and analyzed by a computer.

(3) Analysis of detection results

As shown in fig. 14, the borehole electromagnetic wave imaging apparatus measures stable signals in the occlusive piles with a distance of 30m, and records the information of the positions, the number, the sizes, the shapes and the like of the leakage points detected by the apparatus.

It should be understood that the specific order or hierarchy of steps in the processes disclosed is an example of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged without departing from the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not intended to be limited to the specific order or hierarchy presented.

In the foregoing detailed description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the subject matter require more features than are expressly recited in each claim. Rather, as the following claims reflect, invention lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. To those skilled in the art; various modifications to these embodiments will be readily apparent, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the embodiments described herein are intended to embrace all such alterations, modifications and variations that fall within the scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim. Furthermore, any use of the term "or" in the specification of the claims is intended to mean a "non-exclusive or".

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method of constructing a spud pile having independent pilot tunnels, wherein the retaining wall piles comprise vegetable piles and meat piles which are alternately arranged, the spud pile is formed by mutually spud-in adjacent retaining wall piles, and the formed spud pile is used for an undercut pit foundation retaining wall, the method comprising:

2. A method of constructing a secant pile with independent pilot tunnels according to claim 1, wherein excavating the corresponding pilot tunnel before each secant pile construction according to each retaining pile construction sequence comprises:

3. A method of constructing a secant pile with independent pilot tunnels according to claim 2, wherein the step of reinforcing the pilot tunnel being excavated by welding ring beams and grids comprises:

4. A method for constructing an occlusive pile with an independent pilot tunnel according to claim 2, wherein the plain pile is constructed according to a construction sequence of one-out-of-three construction, specifically comprising:

5. A method for constructing an occlusive pile with an independent pilot tunnel according to claim 4, wherein the plain pile is constructed according to a construction sequence of one-out-of-three construction, specifically comprising:

6. A method for constructing a secant pile with an independent pilot tunnel according to claim 5, wherein the step of sequentially constructing the stage piles comprises the following steps:

7. A method for constructing a secant pile with an independent pilot tunnel according to claim 6, wherein the step of sequentially constructing the stage piles comprises the following steps:

8. A method of constructing a bite pile with an independent pilot tunnel according to claim 7, further comprising:

when the concrete reaches the preset strength, the meat-bearing pile is formed.

9. A method of constructing a bite pile with an independent pilot tunnel according to claim 8, further comprising:

10. A method for constructing a bite pile with an independent pilot tunnel according to claim 1, wherein the cross section of each meat pile is overlapped with the cross sections of two adjacent plain piles respectively, comprising:

the lap length between each meat pile and one engaged vegetable pile is 1/5-1/4 of the diameter of the retaining wall pile; and/or each meat pile and the centers of the two engaged vegetable piles form a straight line.